Process for preparing dioctyltin maleate



United States Patent 3,523,961 PROCESS FOR PREPARING DIOCTYLTIN MALEATEJustin L. Hirshman, East Brunswick, and Edward J. Breza, Fords, N.J.,assignors to M & T Chemicals Inc., New York, N.Y., a corporation ofDelaware No Drawing. Filed Jan. 2, 1968, Ser. No. 694,836 Int. Cl. C07157/22 US. Cl. 260-429.7 19 Claims ABSTRACT OF THE DISCLOSURE Inaccordance with certain of its aspects, the process of this inventionfor preparing dioctyltin dicarboxylate may comprise reactingsubstantially stoichiometric amounts of dioctyltin oxide anddicarboxylic acid or dicarboxylic anhydride in the presence of an inertaliphatic hydrocarbon solvent as reaction medium thereby formingdioctyltin dicarboxylate; cooling said reaction medium after completionof said reaction thereby crystallizing said dioctyltin dicarboxylate;recovering said crystallized dioctyltin dicarboxylate as product; andmaintaining said inert aliphatic hydrocarbon solvent in liquid phaseduring said recovery.

This invention relates to a novel process for preparing organotincompounds. More specifically it relates to a novel process for preparingthese compounds particularly characterized by the ease of obtainingdesired compounds in high purity.

In accordance with certain of its aspects, the process of this inventionfor preparing dioctyltin dicarboxylate may comprise reactingsubstantially stoichiometric amounts of dioctyltin oxide anddicarboxylic acid or dicarboxylic anhydride in the presence of an inertaliphatic hydrocarbon solvent as reaction medium thereby formingdioctyltin dicarboxylate; cooling said reaction medium after completionof said reaction thereby crystallizing said dioctyltin dicarboxylate;recovering said crystallized dioctyltin dicarboxylate as product; andmaintaining said inert aliphatic hydrocarbon solvent in liquid phaseduring said recovery.

The dicarboxylic acids which may typically be employed in practice ofthis invention may include alkylene dicarboxylic acids such as adipicacid or succinic acid or alkenylene dicarboxylic acids such as maleicacid. The corresponding acid anhydride may be employed vis. succinicanhydride, adipic anhydride, maleic anhydride, etc.

The preferred maleic anhydride which may be employed in practice of thisinvention may be that commercially obtainable. If desired, maleic acidmay be employed in place of and as the equivalent of maleic anhydride.

The diocyltin oxide which may be employed in practice of this inventionmay be di-n-octyltin oxide, or di-i-octyltin oxide, di-2-ethylhexyltinoxide, etc. The preferred reactant in practice of the process of thisinvention may be di-n-octyltin oxide. This oxide may be typicallyobtainable in purity of at least 95% having a water content of less than1%.

The inert aliphatic hydrocarbon solvent which may be employed inpractice of this invention as the reaction medium may include thosehaving 5-16 and preferably 6-8, say 7 carbon atoms in the molecule.Typical of these straight-chain or branched chain inert aliphaticsolvents may be alkanes including hexane, heptane, octane, nonane,decane, etc. Cycloaliphatic solvents including cyclohex- Patented Aug.11, 1970 ane, cyclohexene, methylcyclohexane, ethylcyclohexane,1,2-dimethylcyclohexane, etc., may also be employed. In practice of thepreferred aspects of this invention, saturated aliphatic straight chainhydrocarbon solvents may be employed. Preferably the inert aliphatichydrocarbon solvent may be one having a boiling point of at least aboutC. (and preferably above the melting point of the anhydride employed)and less than about 150 C. The preferred solvent may be one having aboiling point about C., preferably about C., and preferably heptane.Various isomers or mixtures of these solvents may be employed.Commercially obtainable mixtures such as commercial heptane (i.e. acommercial heptane having a boiling point of about 99 C.); commercialisoparaifinic mixtures having a boiling range of 126 C.l43 C. (such asIsopar E solvent) may be used. Inert aliphatic hydrocarbon solventcontaining small amounts of other solvents may also be employed, but forattainment of the maximum advantages of the process of this invention,it is preferred to use substantially pure inert aliphatic hydrocarbonsolvent preferably in anhydrous form. Aromatic solvents such as benzene,toluene, etc., should preferably be present, if at all, in amount lessthan 5%, and more preferably less than 1%.

In carrying out the process of this invention according to certain ofits aspects, 70 to parts, preferably 100 parts, of inert aliphatichydrocarbon solvent, preferably heptane may be added to a reactionvessel. 27.2-27.8, preferably 27.6 parts, of maleic anhydride (orequivalent molar amounts of other dicarboxylic acids or anhydrides) maythen be added to the reaction vessel. The ratio of solvent todicarboxylic acid or anhydride may be such as to permit solubility ofthe reaction product in the solvent at elevated temperature andcrystallization at recovery temperature. The preferred ratio of solventto maleic anhydride may be maintained at 2.5 :1 to 5 :1, preferably 2.7:1 by weight as this permits proper solubility of the product in thesolvent at elevated temperatures and maximum crystallization at recoverytemperatures. This ensures maintenance of the desired ratio of solventto product of 0.55:1 to 2:1, say 0.6:1.

The reaction mixture may be heated to above the melting point of theacid or anhydride. When the acid is used, the system may be heated toreflux to remove the water formed. The reaction mixture may preferablybe heated above the melting point of the anhydride-in the case of maleicanhydride, to 60 C.70 0, preferably 65 C., at which point the maleicanhydride may become molten. Agitation may be provided preferably whenthe melting point (60 C.) is reached.

After the dicarboxylic acid, e.g. the maleic anhydride, is substantiallycompletely melted, the dioctyltin oxide in amount of 100-105 parts, say100 parts, may be added to the reaction vessel.

The amount of the dioctyltin oxide to be employed may preferably besubstantially stoichiometrically equivalent to the dicarboxylic acid oranhydride, e.g. in the case of maleic anhydride in accordance with thefollowing reaction:

wherein n is 2-4.

In the case of maleic acid, the reaction may be:

OCO-CH wherein n is 2-4.

Preferably the dioctyltin oxide may be added to the reaction vessel inaliquots of 5%-10%, say 5% of the total amount to be added. When thereaction is with acid, it may preferably be added all at the beginningof the reaction. During addition, the temperature of the reactionmixture may be maintained at about the melting point of the anhydride,typically 70'' C.75 0., preferably 75 C. for maleic anhydride. Additionof the aliquots of ioctyltin oxide may be carried out over 20 minutes-40minutes, preferably 30 minutes. After the completion of the addition tothe reaction mixture of the dioctyltin oxide, the reaction mixture maybe maintained at reflux temperatures below about 130 C. and preferablyat 70 C.l30 C., say 85 C., for 30 minutes-90 minutes, typically 60minutes, for the reaction mixture containing maleic anhydride anddi-n-octyltin oxide. During the reaction, the resulting solution may bevery turbid and amber colored. When maleic acid is employed, thebyproduct water may be removed by azeotropic distillation during thisperiod.

At the end of this reaction, there may preferably be added to thereaction mixture filter medium such as diatomaceous earth; and themixture may be agitated for 5 min.l5 min., preferably 5 min., and cooled(depending on the solvent) to temperature of 45 C.l C., preferably aboutC.-2S C. above the crystallization point. The so-cooled mixture may thenbe filtered at this temperature through a filter, e.g. a pressurefilter, the temperature in which may preferably be controlled duringfiltration to be about 20 C. C. above the point of crystallization-typically 60 C.-l00 C.

The filtrate may thereafter be cooled slowly to room temperature overmin. 120 min., preferably 90 min. with agitation. At the end of thisperiod, the temperature of the reaction mixture may be 20 C.-30 C., say25 C. As the reaction mixture temperature passes through the regionC.-65 C., crystallization may occur; and a thick slurry may be obtainedwhich may be optionally thinned with solvent. The slurry may then befurther cooled to 15 C.-25 C., preferably 20 C. and held at thattemperature for 30 min-90 min., say 60 min. After crystallization, 20-60parts of additional solvent may be added to the slurry to obtain a morefluid consistency. Cooling of the reaction mixture unexpectedly permitscrystallization of the dioctyltin carboxylate product in pure form as aslurry of finely-divided, rod-shaped (when viewed under a microscope)crystals which may be recovered as by filtration or decantation. Duringrecovery of the product, the inert aliphatic hydrocarbon solvent ismaintained in liquid form and the crystals are not subjected to thedeteriorative or disaggregative forces which would undesirably bepresent at higher temperatures characteristic of e.g. distillation. Theformation of distinct individual crystals is desirable and important foreffective and rapid filtration.

The crystalline product may then be separated, e.g. decanted orpreferably centrifuged, from the solvent to recover substantially purecrystalline filter cake which may be washed with fresh inert aliphatichydrocarbon solvent and thereafter spin dried. The cake may preferablybe broken up and dried at 50 C.60 C., preferably 60 C.

The product dioctyltin dicarboxylate may be obtained as off-white tocream colored crystalline powders in yields normally greater than 95%and typically approaching stoichiometric. Commonly, the yields may be90%- 98%. Analysis of typical products may indicate that they containsubstantially the calculated amount of tin and that they have an acidnumber which is essentially that calculated. These products also havemelting points which fall within sharp narrowly defined ranges.

The preferred product dioctyltin maleate may be obtained as an off-whiteto cream colored crystalline powder in yields normally greater than andtypically approaching stoichiometric. Commonly the yields may be %98%.Analysis of a typical product so prepared may indicate that it maycontain 24.95%26.4%, say 25.9% tin (calc. 25.96%). The saponification(i.e. acid) number may be 234-250, say 245 (calc. 244). The product maybe found to have (for di-n-octyltin maleate) a melting point of 93 C.96C.

The novel dioctyltin dicarboxylates of this invention may typically beobtained as substantially pure, freeflowing materials having anoff-white to cream color. superficially the product may be in the formof a powder.

Observation under a microscope may reveal the presence of crystals whichare typically orthorhombic prisms. In the case of the noveldi-n-octyltin maleate, the product may, depending upon the solvent, beobserved in the form of hexagonal prisms. The prisms are characterizedby an X-ray diffraction pattern which indicates characteristic peaks. Inthe case of the preferred di-n-octyltin maleate, the peaks may be foundat 13.6 A., 6.86 A. and 4.6 A. in a wide variety of solvents, includingcyclohexane, Isopar-E, or Solvent 210. In the case of di-n-octyltinadipate, the X-ray spectrum may have peaks at 12.4, 4.12, 6.31, 3.51,8.05, and 4.56 A. (in order of decreasing intensity). In the case ofdioctyltin succinate, the X-ray peaks in order of decreasing intensitymay be 13.7, 6.69, 4.48, 4.74, 4.27, 8.3, 7.89, and 3.37 A.

These products may typically have a sharp melting point over a narrowrange. In the case of di-n-octyltin maleate, the melting point may be93.5 C.95.5 C.

The solubility of these materials may vary. Typical is that of thedi-n-octyltin maleate which may be soluble in warm aromatichydrocarbons, hot aliphatic solvents such as heptane, and cold ketonessuch as methyl ethyl ketone.

Determination of the molecular weight of these novel compositions may becarried out by osmometric technique wherein the compositions may bedissolved in benzene. It is unexpected to find that these materials mayhave molecular Weights which are 2-4 times that of the formula weight.Commonly, they may typically possess molecular weights which may vary onrecrystallization. In one instance, for example, molecular weightchanged from 3.65 formula weights to 2.67 formula weights afterrecrystallization from heptaue.

Practice of the process of this invention will be ap parent from thefollowing examples wherein, unless otherwise indicated, all parts areparts by weight.

EXAMPLE 1 In this example, which represents practice of a preferredembodiment of the process of this invention, 2,200 parts by weight ofcommercially available heptane low in aromatic hydrocarbon may be addedto a reaction vessel together with 810 parts 8.25 moles) of maleicanhydride. The reaction mixture may be heated to 60 C.65 C. and stirringstarted as soon as the maleic anhydride is sufiicien'tly molten to' bestirred. After the maleic anhydride is almost completely molten, theremay be added to the reaction vessel 2,980 parts (8.25 M) of dinoctyltinoxide. Preferably the di-n-octyltin oxide is added in aliquots of 5% ofthe totalt.he typical aliquot being 180-200 parts by Weight. Addition ofthis material may be controlled in manner to keep the temperature at 70C.75 C. Preferably addition may be carried out over 20-40 minutes.Addition of di-n-octyltin oxide at this rate over this period of timemay be sufficient to permit 1naintenance of the reaction mixture influid condition. After the oxide has been completely added to thereaction mixture, the reaction mixture may be further agitated for anadditional hour at 80 C.-85 C. During this time, the reaction mixturemay become amber colored and very turbid.

At the end of 60 minutes, diatomaceous earth filter aid in amount of 0.2part by Weight, may be added to the reaction mixture which maythereafter be agitated for 5 minutes more while being allowed to cool to65 C. The reaction mixture may then be filtered through a preheatedpressure filter maintained at temperature of 60 C.70 C.

The filtered solution may be slowly cooled to room temperature over 90minutes with agitation. As the filtrate cools to 35 C.-40 C.crystallization may occur (with a mild exotherm) and the reactionmixture may become thick at 30 C. An additional 688-800 parts of solventmay be added at this point to thin the slurry to a more fluidconsistency. Further cooling may then be carried out to C. at whichtemperature, the mixture may be held for one hour. The so-cooled mixturemay be filtered and the filter cake washed with 300 parts by weight ofsolvent and thereafter spun dry.

The filter cake which may easily be broken up may be recovered and thendried at 50 C.-60 C. The product so obtained may be 3,411 parts byWeight (90.6% yield) of a product di-n-octyltin maleate having a meltingpoint of 93 C.96 C. and a tin content of 26.15% (theory 25.86%). Theacid number may be 245 (theory 244).

EXAMPLE 2 In this example, which represents practice of an alternativeembodiment of the process of this invention, 2,930 parts by weight ofIsopar E solvent (commercially available mixture of C isoparaflins) maybe added to a reaction vessel together With 817 parts (8.33 moles) ofmaleic anhydride. The reaction mixture may be heated to 60 C.65 C. andstirring started as soon as the maleic anhydride is sufficiently moltento be stirred. After the maleic anhydride is almost completely molten,there may be added to the reaction vessel 2,980 parts (8.25 moles) ofdi-n-octyltin oxide. Preferably the di-n-octyltin oxide is added inaliquots of 5% of the total-the typical aliquot being 180-200 parts byweight. Addition of this material may be controlled in manner to keepthe temperature at 70 C.-75 C. Preferably addition may be carried outover -40 minutes. Addition of di-n-octyltin oxide at this rate over thisperiod of time may be sufficient to permit maintenance of the reactionmixture in fluid condition. After the oxide has been completely added tothe reaction mixture, the reaction mixture may be further agitated foran additional hour at 85 C.95 C. During this time, the reaction mixturemay become amber colored and very turbid.

At the end of 60 minutes, diatomaceous earth filter aid in amount of 0.2part by weight may be added to the reaction mixture which may thereafterbe agitated for 5 minutes more while being allowed to cool at 65 C. Thereaction mixture may then be filtered through a preheated pressurefilter maintained at temperature of 60 C.- 70 C.

The filtered solution may be slowly cooled to room temperature over 90minutes with agitation. As the filtrate cools to 35 C.-40 C.,crystallization may occur and the reaction mixture may become thick at30 C. An additional 200-400 parts of solvent may be added to thin theslurry to a more fluid consistency. Further cooling may then be carriedout to 15 C. at which temperature, the mixture may be held for one hour.The so-cooled mixture may be filtered and the filter cake washed with300 parts by weight of solvent and thereafter spun dry.

The filter cake which may easily be broken up may be recovered and thendried at 50 C.-60 C. The product so obtained may be 3,690 parts byweight (98.5% yield) 6 of a product di-n-octyltin maleate having amelting point of 93 C.-95 C., and a tin content of 25.8% (theory 25.86%The acid number may be 249 (theory 244).

EXAMPLE 3 In this example which represents practice of an alternativeembodiment of the process of this invention, 2,200 parts by weight ofcyclohexane may be added to a reaction vessel together with 817 parts(8.33 moles) of maleic anhydride. The reaction mixture may be heated to60 C.-65 C. and stirring started as soon as the maleic anhydride issufficiently molten to be stirred. After the maleic anhydride is almostcompletely molten, there may be added to the reaction vessel 2,980 parts(8.25 moles) of dioctyltin oxide. Preferably the dioctyltin oxide isadded in aliquots of 5% of the tota1the typical aliquot being 180-200parts by weight. Addition of this material may be controlled in mannerto keep the temperature at 70 C.-75 C. Preferably addition may becarried out of 20-40 minutes. Addition of oxide at this rate over thisperiod of time may be sufficient to permit maintenance of the reactionmixture in fluid condition. After the oxide has been completely added tothe reaction mixture, the reaction mixture may be further agitated foran additional hour at C. During this time, the reaction mixture maybecome amber colored and very turbid.

At the end of 60 minutes, diatomaceous earth filter aid in amount of 0.2part by weight may be added to the reaction mixture which may thereafterbe agitated for 5 minutes more while being allowed to cool at 65 C. Thereaction mixture may then be filtered through a preheated pressurefilter maintained at temperature of 60 C.- 70 C.

The filtered solution may be slowly cooled to room temperature overminutes with agitation. As the filtrate cools to 35 C.-40 C.,crystallization may occur and the reaction mixture may become thick at30 C. An additional 600-800 parts of solvent may be added to thin thesolvent to a more fluid consistency. Further cooling may then be carriedout to 15 C. at which temperature, the mixture may be filtered and thefilter cake washed with 300 parts by weight of solvent and thereafterspun dry.

The filter cake which may easily be broken up may be recovered and thendried at 50 C.60 C. The product so obtained may be 3,560 parts by weight(90.6% yield) of a product dioctyltin maleate, having a melting point of93 C.-95 C. and a tin content of 25.54% (theory 25.86% The acid numbermay be 246.7 (theory 244).

From the above examples, it will be apparent that it is possible bypractice of this novel process to obtain pure dioctyltin maleatesdirectly from a reaction mixture by crystallization. It is not necessaryeither to distill off solvent or to age the product for extended periodof time or to redistill the product in order to obtain the desiredpurity-as is typical of the prior art processes heretofore employed toproduce this material.

EXAMPLE 4 In this example, which represents the practice of a preferredembodiment of the process of this invention, 150 parts by weight of acommercial heptane may be added to a reaction vessel together with 40.4parts (0.277 M) of adipic acid. parts of di-n-octyltin oxide may beadded. The reaction mixture may be heated to reflux (85 C.). The waterof reaction may be removed over 200 minutes by condensation in a DeanStark apparatus. Temperature of reaction then rose to 97 C. after 5parts was collected. A clear yellow solution was obtained. The solutionwas cooled to 75 C. and 0.2 part of diatomaceous earth was added. Thesolution was filtered and cooled slowly. Crystallization occurred at 43C.

An exotherm occurred raising the temperature to 52 C. 50 parts ofheptane may be added and the mixture cooled to ambient temperature overone hour. The socooled mixture may be filtered and the filter cakewashed with a small amount of solvent and thereafter dried.

The filter cake which may easily be broken up may be recovered and driedat 50 C.60 C. The product so obtained may be 129.4 parts by weight(95.6% yield) of a product having a melting point of 75 C. and a tin content of 24.26% (theor 24.26%). The acid number may be 240 (theory 229).

The molecular weight (osmometric in chloroform) was 692.

EXAMPLE In this example, which represents practice of a preferredembodiment of the process of this invention, 75 parts by weight ofIsopar E (a commercially available mixture of iso-octanes) may he addedto a reaction vessel together with 28.2 parts (0.28 M) of succinicanhydride. The reaction mixture may be heated to 120 C. and stirringstarted as soon as the anhydride is sufliciently molten to be stirred.After the anhydride is almost completely molten, there may be added tothe reaction vessel 100 parts (0.28 M) of di-n-octyltin oxide.Preferably the di-noctyltin oxide is added in aliquots of of the totalover 30 minutes. Addition of dioctyltin oxide at this rate over thisperiod of time may be sufiicient to permit main tenance of the reactionmixture in fluid condition. After the oxide has been completely added tothe reaction mixture, the reaction mixture may be further agitated foran additional hour at reflux temperature of 135 C., which temperaturewas reached after 90 minutes. At this time, the reaction mixture maybecome clear.

The mixture may be cooled to 120 C.-l25 C. and dicalite filter aid inamount of 0.2 part by weight may be added to the reaction mixture whichmay thereafter be filtered through a preheated pressure filtermaintained at temperature of 125 C.

The filtered solution may be slowly cooled over 30 minutes withagitation. As the filtrate cools to 106 C., crystallization may occur.100 parts of additional solvent may be added. Further cooling may thenbe carried out to C. at which temperature, the mixture may be filteredand the filter cake washed with a small amount of solvent Isopar E andthereafter dried.

The filter cake which may easily be broken up may be recovered and driedat 50 C. The product so obtained may be 123.6 parts by weight (97%yield) of a product having a melting point of 140 C., and a tin contentof 25.71% (theory 25.74%). The acid number may be 240 (theory 243).

The molecular weight (osmometric in chloroform) was 954.

Although this invention has been illustrated by reference to specificexamples, changes therein which clearly fall within the scope of thisinvention will be apparent to those skilled-in-the-art.

What is claimed is:

1. The process for preparing dioctyltin dicarboxylate which comprisesreacting substantially stoichiometric amounts of dioctyltin oxide anddicarboxylic acid or dicarboxylic anhydride in the presence of an inertaliphatic hydrocarbon solvent in which said dioctyltin oxide, saiddicarboxylic acid, and said dicarboxylic anhydride are insoluble and inwhich dioctyltin carboxylate is soluble as reaction medium therebyforming a solution of dioctyltin dicarboxylate in said solvent; coolingsaid reaction medium after completion of said reaction therebycrystalliz ing said dioctyltin dicarboxylate; recovering saidcrystallized dioctyltin dicarboxylate as product; and maintaining saidinert aliphatic hydrocarbon solvent in liquid phase during saidrecovery.

2. The process for preparing dioctyltin maleate which comprises reactingsubstantially stoichiometric amounts of maleic anhydride and dioctyltinoxide in the presence of an inert aliphatic hydrocarbon solvent in whichsaid dioctyltin oxide and said maleic anhydride are insoluble and inwhich dioctyltin maleate is soluble as reaction medium thereby forming asolution of dioctyltin maleate in said solvent; cooling said solutionafter completion of said reaction thereby crystallizing said dioctyltinmaleate; filtering said crystallized dioctyltin maleate; and maintainingsaid inert aliphatic hydrocarbon solvent in liquid phase during saidfiltration.

3. The process of claim 2 wherein said doctyltin oxide and maleicanhydride are reacted at a temperature above the boiling point of thesolvent and between about 60 C. and C. in a solvent selected from thegroup consisting of heptane, and isoparafiinic hydrocarbon solventhaving a boiling point above the reaction temperature and below aboutC.; the ratio of said solvent to the product dioctyltin maleate beingbetween 0.55:1 and 2:1; and cooling said solution of dioctyltin maleateat a temperature between about 15 C. and 40 C. to crystallize saidproduct dioctyltin maleate.

4. The process of claim 3 wherein said solvent is heptane.

5. The process for preparing dioctyltin dicarboxylate which comprisesreacting dicarboxylic acid or dicarboxylic anhydride and dioctyltinoxide in the presence of an inert aliphatic hydrocarbon solvent, inwhich said dioctyltin oxide and the dicarboxylic reactant are insolubleand in which dioctyltin dicarboxylate is soluble, as reaction mediumthereby forming a solution of dioctyltin dicarboxylate in said solvent;filtering said solution to remove any unreacted dioctyltin oxide anddicarboxylate reactant; then cooling said solution thereby crystallizingsaid dioctyltin dicarboxylate, and recovering said crystallinedioctyltin dicarboxylate from said liquid solvent which is maintained inliquid phase during said recovery.

6. The process for preparing dioctyltin maleate which comprises reactingmaleic anhydride and dioctyltin oxide in the presence of an inertaliphatic hydrocarbon solvent in which maleic anhydride and dioctyltinoxide are insoluble and in which dioctyltin maleate is soluble asreaction medium thereby forming a solution of dioctyltin maleate in saidsolution; filtering said solution to remove any unreacted dioctyltinoxide and maleic anhydride; then cooling said solution therebycrystallizing said dioctyltin maleate; and recovering the crystallinedioctyltin maleate from said liquid solvent which is maintained inliquid phase during said recovery.

7. The process of claim 6 wherein said dioctyltin oxide and maleicanhydride are reacted at a temperature above the boiling point of thesolvent and between about 60 C. and 100 C. in a solvent selected fromthe group consisting of heptane, and isoparaflinic hydrocarbon solventhaving a boiling point above the reaction temperature and below about150 C.; the ratio of said solvent to the product dioctyltin maleatebeing between 0.55 :1 and 2:1; and cooling said solution of dioctyltinmaleate to a temperature between about 15 C. and 40 C. to crystallizesaid product dioctyltin maleate.

8. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein, after completion of reaction, said reaction medium iscooled to 15 C.-40 C. at which temperature said dioctyltin maleate maybe removed in crystalline form.

9. The process of claim 7 wherein said solvent is heptane.

10. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein said inert aliphatic hydrocarbon solvent contains 5-16carbon atoms.

11. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein said inert aliphatic hydrocarbon solvent contains 6-8carbon atoms.

'12. The process for preparing anhydrous dioctyltin maleate as claimedin claim 6 wherein said inert aliphatic hydrocarbon solvent is astraight chain aliphatic hydrocarbon solvent.

13. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein said inert aliphatic hydrocarbon solvent is heptane.

14. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein said inert aliphatic 9 hydrocarbon solvent 'has aboiling point of less than 150 C.

15. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein said inert aliphatic hydrocarbon solvent is anisoparatfinic hydrocarbon.

16. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein the temperature of reaction is maintained at about 60 C.

17. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein the temperature of reaction is maintained below 130 C.

18. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein the temperature of reaction is maintained at 60 C.-100C.

19. The process for preparing anhydrous dioctyltin maleate as claimed inclaim 6 wherein the ratio of solvent to product is maintained at 0.55 :1to 2:1.

References Cited UNITED STATES PATENTS Weisfeld et al. 260429.7 Oakes260429.7 Katsumura et al. 260429.7 Gloskey 260429.7 Duyfjes et al.260429.7 X Crauland 260429.7 X Anderson et al. 260429.7 Anderson et al.260429.7 X Robins 260429.7 X Kelso 260429.7 X 'Kelso 260429.7 X

15 HELEN M. McCARTHY, Primary Examiner W. F. W. BELLAMY, AssistantExaminer

